Yes, I believe that extraterrestrial life exists and that we are not alone in the Universe. Indeed, given the vast extent of the Universe and the relatively simple nature of the organic molecules necessary to form living things, it would be foolish to believe otherwise. It is a virtual certainty that life exists on other planets - most likely in abundance.
No, however, I don't believe that any of those extraterrestrial beings have ever visited the Earth in flying saucers - and certainly not in the vast numbers claimed by UFO cultists.
The term "UFO" itself has come to be synonymous with alien spacecraft, or "flying saucers". In reality, of course, a "UFO" is nothing more or less than an "Unidentified Flying Object". In short, this means that anything in the sky that an observer can't identify is a UFO. This encompasses everything from clouds to birds to natural phenomena to test flights of new aircraft to, if they existed, "flying saucers".
The fact that people see "strange" things in the sky is testimony only to their ignorance and not proof that we are being visited by extraterrestrial civilizations. Even when these sights are fully explained (or even predicted, in the case of meteor showers), there is a segment of the population that doggedly hangs on to its beliefs. This shouldn't come as any great surprise, however, since it seems to be normal for people to continue to believe in whatever they wish despite any
and all evidence to the contrary.
Many people point to "military coverups" as some sort of proof that their "flying saucer" stories have some validity. The current explosion of UFO hysteria coincides with the beginning of the military's research and testing programs with jet aircraft after the end of World War II. These programs are all Top Secret (or higher) and, by regulations, can't be declassified for at least 75 years. At times, test flights of strange new aircraft are witnessed by the public and the inevitable "flying saucer" stories start up. Since the military cannot conclusively debunk those stories without compromising classified information, the stories often go unchallenged and, therefore, gain acceptance. Of course, this doesn't make the stories any more valid, but that point seems lost on those who believe in them.
So, the next time you hear another UFO story, take the time to see if there's any concrete evidence to back up any claim that it was a "flying saucer". Until such evidence is presented, the phenomenon should be interpreted for what it is -- an Unidentified Flying Object.